Home air quality
How to test the air quality in your home.
Testing the air quality in your home means measuring the pollutants and conditions your body is actually exposed to — fine particles, carbon dioxide, chemical vapours and humidity — and reading them against healthy ranges. Air is the one pillar of a healthy home that changes hour by hour, which makes it the one worth measuring rather than guessing at.
What to measure
The six numbers that describe your air.
PM2.5 — fine particulate
µg/m³
Particles small enough to reach deep into the lungs and enter the bloodstream. Driven by outdoor air, cooking, candles and combustion, and filtered by the home's air handling. The WHO annual guideline sits at 5 µg/m³, so lower is always better than the band suggests.
CO₂ — carbon dioxide
ppm
Not a pollutant at household levels — a proxy for fresh-air supply. Outdoor air sits near 420 ppm; a sealed bedroom overnight routinely climbs past 2,000. Higher values track with stale air, stuffiness and reduced concentration. This is the single most useful number in a bedroom.
TVOC — total volatile organic compounds
µg/m³
The combined off-gassing of paints, adhesives, boards, furnishings and cleaning products. It peaks after painting or new furniture and falls over the first months. A number that should be trending down — if it is not, something indoors is emitting continuously.
Humidity
% RH
Relative humidity below 40% dries airways and timber; persistently above 60% feeds dust mites and, at cold surfaces, condensation and mould. Measured at the coldest room — usually the bedroom — it is also the earliest mould indicator in a home.
Carbon monoxide
ppm
Colourless and odourless, from gas heaters, fireplaces and flues. A CO alarm is not optional — it is the one monitor every home with combustion appliances should have running permanently.
Radon
Bq/m³
A naturally occurring radioactive gas from soil under the building, relevant in particular Australian regions and geological settings. A short-term detector gives an indication; a long-term test over months is the one that matters. Worth testing once, especially in a slab-on-ground home.
Ranges shown are the bands we certify against, drawn from WHO air-quality guidance, ASHRAE 62.1 and Building Biology sleeping-area guidance. They are judgement aids, not a diagnosis of any single reading.
Two ways to test
A monitor on the shelf, or instruments in the room.
Consumer monitors give continuous awareness, and that alone is worth having. A CO₂ monitor in the bedroom teaches most people more about their home in a week than years of guessing: the room that never drops below 1,200 ppm overnight, the humidity that climbs when the door stays shut. They are less reliable than they look, though — cheap sensors drift, particle sensors estimate rather than measure, and none of them tell you what a VOC reading is actually made of.
A professional assessment answers the questions monitors cannot: instruments that are calibrated and traceable, placed where they matter and read under the conditions your life actually creates — bedroom overnight in a normal winter, kitchen during and after cooking, and every occupied room in between. It adds the layer that turns numbers into answers: identifying sources, tracing moisture, and connecting a reading to the building detail that caused it.
Our own view is that both belong in a healthy home: monitoring for daily awareness, and building biology for the diagnosis beneath it.
Reading the results
What your numbers are telling you.
High CO₂ is the ventilation verdict. It rises and falls with the people in the room and the air you supply them, and no filter or plant changes it — only dilution does. If the bedroom cannot hold 800 ppm overnight, the home’s fresh-air supply is the conversation, not the mattress.
Rising TVOC is a source verdict. Something in the room is emitting — a finish, a fabric, a cabinet, a habit. Source control, then ventilation, then filtration, in that order.
Humidity out of range is a moisture verdict, and it connects directly to how mould starts. High humidity at cold surfaces is condensation arriving on schedule; treat the building, not the symptom.
PM2.5 splits by origin: outdoor air, cooking, candles and combustion each leave a signature. Filtration helps with what arrives from outside; behaviour and extraction change what is generated inside.
The bigger picture
Testing answers questions. Design stops them being asked.
Every reading on this page is influenced by decisions a home makes before anyone moves in: ventilation sized and balanced for how the home is used, materials selected for what they emit over years, filtration and humidity control built into the air system rather than bought as an appliance afterwards. That is the air pillar of the Homey Standard — air treated as a designed system, not an afterthought.
For an existing home, measurement is the honest first step, and remediation is genuinely available — ventilation upgrades, filtration, humidity control, and finishing materials that stop emitting. It is a better project than most people expect, because the causes are usually few and findable.
For a new home, the same measurements become a record. At handover, air quality and VOC readings are taken through the finished building — once the finishes are in, when off-gassing actually shows up — and recorded pillar by pillar in the home’s certification. The certificate is a written account of what was implemented against each of the eight pillars and what was not, so a buyer or guest never has to take anyone’s word for how a home was built.
If you are building and want air, moisture and light decided early rather than tested late, that is our consultancy work — and the reason we are in it.